TM 11-6130-247-14-1
tolerance resistor. The voltage drop across resis-
constant at S volts dc. (A3Q20 and A4Q4 act to
tor R52 then represents the current through the
detect any voltage variation across Q13 network
load. This voltage drop is compared to a reference
R37, Q13, R39, and R52.) The A3Q20 base is
voltage (voltage divider R53A and R53B, the
biased by a reference voltage (A3CR20 and
front panel CUR ADJ controls, and R54 and
potentiometer A3R57) at approximately 5 volts
dc below the output voltage.
A3R55, across zener diode A3CR20). The ref-
erence voltage is applied to A3Q1.9 which is one
The emitter of A3Q20 transfers this voltage.
half of differential amplifier A3Q18, A3Q19, and
to the base of Q4. The emitter of A4Q4 senses
associated circuitry. The R52 voltage drop is ap-
the input voltage to the series regulator stage at
plied to A3Q18. Resistor A3R50 is used to bal-
the junction of R33 and R37. Any difference be-
ance the differential amplifier. Any detected er-
tween the base and emitter voltages of A4Q4
ror is applied to a second differential amplifier
will be proportional to the error existing be-
composed of A3Q16, A3Q17, and associated cir-
tween the A3Q20 reference voltage and series
cuitry. The amplifier error signal changes the
stage voltage drop. The collector of A4Q4 de-
collector potential of A3Q16, which changes the
termines the dc bias to the Schmitt trigger
bias of A3Q31 through diodes A3CR24A and
which determines the proper on-off time of the
A3CR24B. Changing the bias of A3Q31 affects
series switch. Thus, the preregulator output volt-
age is corrected so that the Q13 voltage drop is
the bias of Q15, which is the driver of the Dar-
held constant at 5 volts dc.
lington-connected linear series regulator, chang-
ing the impedance of Q13. Transistor Q13 pro-
d. Current Regulation Circuitry. Current is
vides instantaneous correction of the error and
regulated by sensing the voltage drop across re-
thus holds the current constant. The voltage drop
sistor R52. Since resistor R52 is in series with
the output load, the amount of current flowing
across Q13 is held constant by the same method
through the load also flows through this close
discussed in c above
4-4
